UBUNTU-CVE-2026-27588 (CVE-2026-27588)

Vulnerability from osv_ubuntu – Published: 2026-02-24 17:29 – Updated: 2026-07-02 16:11 – Source website
VLAI
Details

Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's HTTP host request matcher is documented as case-insensitive, but when configured with a large host list (>100 entries) it becomes case-sensitive due to an optimized matching path. An attacker can bypass host-based routing and any access controls attached to that route by changing the casing of the Host header. Version 2.11.1 contains a fix for the issue.

Severity
7.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P
9.1 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "caddy",
            "binary_version": "2.6.2-6ubuntu0.24.04.3+esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:24.04:LTS",
        "name": "caddy",
        "purl": "pkg:deb/ubuntu/caddy@2.6.2-6ubuntu0.24.04.3+esm2?arch=source\u0026distro=esm-apps/noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.6.2-6",
        "2.6.2-6ubuntu0.24.04.1",
        "2.6.2-6ubuntu0.24.04.2",
        "2.6.2-6ubuntu0.24.04.2+esm1",
        "2.6.2-6ubuntu0.24.04.3",
        "2.6.2-6ubuntu0.24.04.3+esm1",
        "2.6.2-6ubuntu0.24.04.3+esm2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "caddy",
            "binary_version": "2.6.2-12"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "caddy",
        "purl": "pkg:deb/ubuntu/caddy@2.6.2-12?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.6.2-9",
        "2.6.2-11",
        "2.6.2-12"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "caddy",
            "binary_version": "2.6.2-14ubuntu0.26.04.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:26.04:LTS",
        "name": "caddy",
        "purl": "pkg:deb/ubuntu/caddy@2.6.2-14ubuntu0.26.04.1~esm1?arch=source\u0026distro=esm-apps/resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.6.2-12",
        "2.6.2-14",
        "2.6.2-14ubuntu0.26.04.1~esm1"
      ]
    }
  ],
  "aliases": [],
  "details": "Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy\u0027s HTTP `host` request matcher is documented as case-insensitive, but when configured with a large host list (\u003e100 entries) it becomes case-sensitive due to an optimized matching path. An attacker can bypass host-based routing and any access controls attached to that route by changing the casing of the `Host` header. Version 2.11.1 contains a fix for the issue.",
  "id": "UBUNTU-CVE-2026-27588",
  "modified": "2026-07-02T16:11:59Z",
  "published": "2026-02-24T17:29:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-27588"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-27588"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/caddyserver/caddy/security/advisories/GHSA-x76f-jf84-rqj8"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/caddyserver/caddy/releases/tag/v2.11.1"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P",
      "type": "CVSS_V4"
    },
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-27588"
  ]
}



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